1 White blood cells are one of the four main parts of blood. The other parts are the red blood cells, platelets, and plasma. There are different kinds of white blood cells, but they all have an important job. Do you know what that job is? White blood cells defend the body from infection and disease.2 Some white blood cells go to the places in your body where you have a cut. They attack any bacteria that enter your blood to stop them from spreading throughout your body.3 Some bacteria and viruses that enter your body carry chemicals called antigens. Your white blood cells make their own chemicals called antibodies, which will attach themselves to these antigens so that the poisons from the bacteria or viruses become harmless. Do you know how amazing these cells are? Well, the antibodies that your white blood cells produce only attack the antigen for which it was made. For example, an antibody for the chicken pox virus will only attack the chicken pox virus, not the measles virus. Even more amazing is that the white blood cells in your body remember how to make the antibody in case the germ ever enters your body again!